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I am trying to answer an email I received today about the differences between what he calls a 24vdc alternator and a 12vdc alternator.
Alternators generate AC current until rectified to DC.
I am by no means an expert on this stuff but to me a 24v alternator and a 12v alternator should be the same if you eliminate any voltage regulation and the rectifier correct?
My experience with 24vdc equipment is limited.

The windings, rectifier, rotor, and brushes should be sized for current not voltage correct?
Or is there a relationship between voltage and current that determines winding size etc.?
My unregulated alternator will put out voltages ranging from 1-150vdc depending on the engine rpm.

If the alternator rpm or voltage is low and you strike an arc, the current load on the alternator will be extremely high but if you spin the alternator faster and increase voltage, the amp load on the alternator will be lower correct?
It should be the same as lowering the voltage on an electric motor. Lower the voltage motor and current goes high, increase voltage and the current drops.

A rheostat would control voltage not current if it were wired in the exciter circuit. It would work but to obtain the proper voltage to weld with, the engine still has to be up around 2000 rpm, of course that depends on your alternator speed.
Unless you are burning very small rod however, lower engine rpms or lower voltages are not very useful.
How close am I?
I am not an electrician so give me a break on the terminology.

Trailhed.com
 

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Is this an on the level question?
And do you want me to answer it?

So many cats, so few recipes...
 

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Several years ago, I had a 24v alternator made at a rebuild shop to replace the shorted generator and regulator on my M38A1. The guy at the shop told me that the 24v used different windings as well as a different regulator. I think he said there were more windings with a smaller wire. For $60 (I think, it's been a while) it was way cheaper than $300+ to get a replacement generator and regulator.

 

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Looks like CJ Taz is unhappy with something again...
(Starting personal attacks again)

Well, CJ Taz, the floor is yours...
Lets have your First hand, personal experence in the field of production alternator remanufacture...
 

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team rush wrote: (he deleted his statement later)
It's pretty well accepted as fact that the electrons run down the outside of the wire, not through the center, so finer strands allow for more surface area in the same amount of space.
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hey team rush. I'm not trying to flame you. that crap is for Pirate4X4. but...

I disagree with you previous statement. I believe that 95% of the time, wire is stranded to make it more flexible. But, stranding cost money, so fixed applications like house wiring is a prime candidate for solid core wire, driven by cost. Solid core wire would fatigue and eventually break in a car.

The other 5% of the applications for stranded wire is to change impedance of the wire.

here is a link to cable college on the Belden web site, they make wire, you may find it interesting.
http://bwcecom.belden.com/college/college.htm

if you take the 101 test you will find question 5 interesting.

to get a good understanding of electron flow, I personally think that a college level chemistry book is the way to learn. look for a section on Electro chemistry and voltaic cells. it's all about valance electrons. look at your periodic table, all the metals are in the same column, i.e. same number of valence electrons. but, long story short. the transfer of electrons is all about the ionic bond and happens "atom to atom" and not on the skin of the wire.

there is "the skin effect" but that is only for high frequency stuff.

1989 jeep YJ,4.2L,5spd
"Roger-dodger, putt putt"

http://hometown.aol.com/gouldvolts/jeep/jeep.html
 

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Aaron's right on the electrons traveling along the surface of the wire.

 

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The phenomena of electric current only moving in the outer surface of the conductor is termed shell thickness and is only applicable in very high frequency applications (we're talking gigahertz here).

Free electrons are constantly moving in a piece of wire but in a random motion pattern. Application of an electrical source causes a small percentage of these electrons to move in the desired direction, opposite to conventional current flow.

What you may be thinking of is that only the electrons in the outer, or valence shell, of the molecules are free to move about. Lower shell electrons stay in orbit about the same nucleus. Valence electrons are free to move about by exchange process.


 

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Looks like CJ Taz is unhappy with something again...
(Starting personal attacks again)

Well, CJ Taz, the floor is yours...
Lets have your First hand, personal experence in the field of production alternator remanufacture...
 

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I wish I knew something about welding. but I don't.

But
here is something to read. notice the part where it says, almost noticeable at 60Hz. this is from an EE text book. the book does fail to mention that the skin effect effects AC, pulses or any signal with high frequency components.

1989 jeep YJ,4.2L,5spd
"Roger-dodger, putt putt"

http://hometown.aol.com/gouldvolts/jeep/jeep.html
 

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The electrons moving around, being shared, is covalent bonding. Without it the wire would not hold together. I guess it would turn to gas. Also there would be no water, just oxygen and hydrogen gas.

If you mention the "hole theory" at an electrical engineering cocktail party, you would open a can of worms that would cause an all night debate. Some subscribe, others call it humbug. Personally, I think it's a pretty good way of describing what is going on.

This is a guess, but I think the stranded wire cools better, I know it will carry a little more amperage.

I don't know how to hook up 3-phase for welding unless it's into the motor end of a Hobart MG set welder. I'm guessing you are talking about much lower voltage though.

For skin effect, that's it but to get to a point where the electrons travel only in a thin layer on the surface, the frequency has to get pretty high.


 

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Looks like CJ Taz is unhappy with something again...
(Starting personal attacks again)

Well, CJ Taz, the floor is yours...
Lets have your First hand, personal experence in the field of production alternator remanufacture..
 

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ionic bond is when an electron is actually transferred. covalent is when they are shared. but, you probably already knew that. There is no disagreement, the copper wire will have a covalent bond between the copper atoms.
but... in my defense, I was talking in regards to a voltaic cell. There will be ionic bonds forming on the anode, that is where the free electrons come from.
without the ionic bond we would not have batteries or rust. And with no rust, what would hold all those CJs together?

[] |||||| []

1989 jeep YJ,4.2L,5spd
"Roger-dodger, putt putt"

http://hometown.aol.com/gouldvolts/jeep/jeep.html
 

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What the $#*&% are Anti-Electrons and what do they have to do with hole theory?

My comments about the electron flow in a conductor were in reply to WILL's statement, "Aaron's right on the electrons traveling along the surface of the wire."

I didn't read much of your post. It was way too long and, I took too many exceptions in the little that I did read. I didn't comment on this because you asked;

*I am not an electrician so give me a break on the terminology.*

OK, I'll give you some slack... Do the same for me....
I'm not going to use completely correct terms, and I'm going to bend things a little for the sake of
explanation...
----------------

Besides you get childish and resort to name calling if I disagree with you. Now that your request was honored and nobody haggled with you, you are patting yourself on the back? Nice strategy!

I also resent your comments that you lost half the readers when you mentioned physics and the other half when you mentioned mathematics. I give this board credit for greater collective intelligence than that.

Simply put, if you want to produce electrical energy by conversion, pass a conductor through a magnetic field or hold the conductor stationary and vary the field. Want higher voltage? Increase the number of winding coils or the strength of the field.

You will not produce DC, you must rectify it and even then there is some voltage fluctuation. An alternator uses diodes while a generator uses lots of windings and rectifies it at the commutator.
 

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Speed_buggy, it's been too long since I studied ionic bonding. The rust is ferrous oxide which is covalent (shares electrons), it adheres to the steel through ionic bonding (no shared electrons), right?

I wish you hadn't posted that, now you've got me trying to remember how ferric oxide occurs.


 

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there are 2 main types of chemical bonds.
ionic and covalent. The bond in a binary molecule (only two atoms) will more likely to be ionic, if they are further apart (in the horizontal across) on the periodic table.

In Covalent bond the electron is shared equally. In ionic the electron is completely stripped away and hoarded by one of the atoms.

It is easy to remember if you know what an ion is. (Fe+ ) But the ionic bond is strong.

Warning rust is very complicated, I am only talking about a text book example.

Rust is an oxidation reduction reaction and there is actual electron transfer. The reaction is actually Electro chemical, the same as a battery. Unfortunately the frame of your CJ is the anode so electrons are removed from the iron in your frame. There is an Energy of oxidation value for different elements, the higher it is the easier it oxidizes. You can actually uses a sacrificial anode ( higher E oxidation zn,Mg…) and turn your frame into the cathode. But I don't think that works because the frame is used as a current path for the rest of the electrical system.

I looked this up for you:

2Fe + 02 + H2O --> Fe2O3 * xH20

1989 jeep YJ,4.2L,5spd
"Roger-dodger, putt putt"

http://hometown.aol.com/gouldvolts/jeep/jeep.html
 

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Some of that made sense but I think the elf in chare of that part of my memory is in a comma from too much Miller Lite. I do remember ions and ionic bonding. I remember that ionic bonds are weak with respect to covalent bonds. I remember that I can dump NaCl into water and the ions separate. I also remember that a given amount of water will only support so much salt before it falls to the bottom as crystals.

I also remember that some gases are diatomic H2 and O2 for example. I remember that ozone is O3 and unstable. I remember that I have HCl in my stomach and H2SO4 in my battery. Much past this and I need to go to the net for a refresher. I never took the organic classes so I'm pretty much lost there.

 

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Jeeplvr ...

To answer your question without regard to all the electron flow BS, and assuming identical frame sizes, a 12V alternator and a 24V alternator have different windings.

Output voltage is a function of the number of windings and output current is a function of the wire size used in those windings.

So, given a fixed amount of real estate in the alternator housing, a 12V unit will generally have fewer windings made with bigger wire while the 24V unit of the same frame size will have more windings with a smaller wire size.

BTW, automobile alternators are usually built on 5" frames and truck units on 6.5" or 8.5" frames.

Here's a link to Prestolite/Leece-Neville's site that you might find interesting ... or not.

http://www.prestolite.com/cgi-bin/pei_alt_series.cgi

Rockcrusher
Nevada ORU
http://www.rockcrusher4x4.com
It's a Jeep thing ... At least it was 'til Chrysler took over!
 
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